Automatic controller



y 1937- H. L. VAN VALKENBURG 2,080,241

AUTOMATIC CONTROLLER Filed Dec. 7, 1934 6' f 4 I INVENTOR. E a (5M Hermo 3 ATTORNEY.

Patented May 11, 1937 UNITED STATES PATENT OFFICE AUTOMATIC CONTROLLER Hermon L. Van Valkcnburg, Wauwatosa, Wis.,

assignor to Square D Company, Detroit, Mich,

27 Claims.

This invention relates generally to automatic electric circuit controllers and more particularly to automatic motor starters of the current limit type for starting direct current motors.

Direct current automatic starters of the current limit type are well adapted for several classes of service especially those' in which there is a high inertia load. This type of starter, however, has the disadvantage that the accelerating 1n contactors will not function if the load on the motor exceeds that for which the lockout coils have been adjusted. In other words if the accelerating units have been so adjusted that they will cut out resistance when current drops to a given value they will not operate if for some reason the current will not fall below this current value. One example of an instance wherein this trouble may occur is with motors driving grinders in which a very heavy load may be applied to the grinding-wheel before the motor has been fully brought up to speed. It is obvious that this same trouble may occur for many other reasons in actual practice. Under such conditions the starting resistance will be left in circuit and would be likely to burn out.

Aside from the above difliculty, the characteristics of the current limit starter are very desirable as the motor will be brought up to full speed in the shortest possible time consistent with a given accelerating current. For instance, if a starter is furnished with a resistance so proportioned as to permit a maximum of 100% overload in starting, the motor will then come up to speed in the shortest possible time without exceeding this in-rush current.

To correct the disadvantage above set forth in the current limit starter the invention in one aspect consists in providing a time limit relay for each accelerating unit which will short-circuit the lockout coil after a predetermined interval of time if the accelerating unit does not function.

Another object 'of this invention is to provide an automatic starter embodying combined current and time limit acceleration.

Another object of this invention is to provide an automatic starter operating through current limit acceleration with a relay which will shunt the lockout coil after a predetermined time interval.

A further object of this invention is to provide an automatic starter in which the lockout coil is in series with a self-heating thermal relay which operates to shunt out the lockout coil after a predetermined time interval.

Another object or this invention is to provide an automatic starter of the current limit type using a starting resistance with a protective circuit to prevent burning out of said resistance.

A further object of this invention is to provide an automatic starter of the current limit type in which the lockout coils are connected in shunt across the successive steps of starting resistance and in which a thermal relay is connected in series with the lockout coil, the thermal relay operating to close a shunt circuit for the lockout coil.

Another object of this invention is to provide an improved method of starting motors.

Still another object of this invention is to provide an improved current limit relay having a positive time limit operation. A

Further objects and features of the invention will be readily apparent to those skilled in the art from the following specification and the appended drawing illustrating certain preferred embodiments of the invention in which:

Figure 1 is a schematic wiring diagram showing one embodiment of this invention particularly adapted for use with small motors.

Figure 2 is a schematic wiring diagram of another embodiment of this invention particularly suited for large motors.

Referring now particularly to the embodiment of the invention as shown schematically in Figure 1, the numerals l and 2 designate line terminals. A motor 3 has one side of its armature connected to terminal I by conductor 4. The shunt field 5 is connected across the line by conductors 6 and 1, conductor 6 being connected directly to line i through conductor 4; conductor 1 being connected to one side of main contactor 8 through a connection 9. The main contactor 8 has an actuating coil ll connected across the line terminals by conductors and I! through a switch it. The other side of the armature of motor 3 is connected through a conductor I! to contact I6 and thence to one side of the starting resistance H which, as shown, embodies two steps l8 and IS. The other end of starting resistance 11 is connected by conductor 2| to the lockout coil 22 of the first accelerating step of the starter. The other side of the lookout coil 22 is connected by conductor 23 to one leg of a U-shaped bimetallic member 24, the other leg of which is connected to one side of the main contactor through the connection 9. The tip of bimetallic member 24 carries a contact 25 disposed adjacent to a stationary contact 26 which is connected through conductor 21 to the same side of lockout coil 22 as the conductor 2i. It is thus seen that a shunt circuit across the lockout coil 22 is provided through conductor 23, one leg oi bimetal 24, contacts 25 and 26 and conductor 27. This shunt circuit is normally open and is closed by the fiexure of the thermostatic member 24 as it is heated by the starting current. The main contactor 8 embodies a stationary contact 28 connected to line terminal 2 and a movable contact 29 attracted into engaged position with contact 28 by operating coil H. A movable contact 3| attached to contact 29 and moving therewith is provided. This contact engages a stationary contact 32 to which is connected conductor 33 leading to one side of the shunt operating coil The other side of operating coil 34 is con uected by conductor 35 to switch I4. The coils 34 and 22 constitute a differential solenoid surrounding an armature 38 which carries a conducting member 31 adapted to bridge contacts 38 and 39. Contact 38 is connected by conductor 4| to conductor 9 and thence to main contact 8. Contact 38 is also connected by conductor 42 to Contact 43 which is disposed adjacent to contact i8. Contacts i8 and 43 are adapted to bridge by a conducting member 44 carried by armature 45 under the action of operating coil 48 and lockout coil 41. Operating coil 48 is connected at one side by conductor 48 to switch l4. The other side of the operating coil 48 is connected by conduetor' 49 and the short flexible lead 5| to conducting member 31. Lockout coil 41 is connected at one side by conductor 52 to resistor I! at the junction between steps i8 and IS. The other side of lockout coil 47 is connected through conductor 53 to one leg of bimetallic member 54, the other leg of which is connected by conductor 55 to contact 39. The tip of the bimetallic member 54 carries a contact 58 adapted to engage a stationmy contact 5! disposed adjacent thereto and connected by a wire 58 to the same side of the lockout coil as conductor 52.

The operation of the starter above described is as follows:

Switch I4 is manually closed thus energizing operating coil ii and closing main contactor 8. This energizes operating coil 34 through contacts 3! and 32, conductor 33, coil 34, conductor 35, switch l4 and conductor l3 to the opposite line terminal. At the same time a circuit through the motor armature is initiated from line terminal 2, contacts 28 and 29, conductor 9, bimetal 24, conductor 23, lockout coil 22, conductor 2|, resistance i'l, conductor l5, the armature of motor 3, and conductor 4 to line terminal I. The circuit throughshunt field 5 is completed through contacts 28 and 29, conductor 9, conductor 1, shunt field 5, conductor 8 and conductor 4 to line terminal I. If the motor 3 starts and builds up speed, the starting current will rapidly decrease and the lookout coil 22 will no longer be suflicient to counteract the tendency of operating coil 34 to move armature 36 which then moves bridging member 31 into engagement with contacts 38 and 39 cutting out step l8 of the starting resistance ll. This also shunts out the circuit through lockout coil 22 and bimetal 24. The circuit through the motor armature then runs from line 8 to line H thence through contact 38 and bridging member 31, contact 39, conductor 55, bimetal 54, conductor 53, lockout coil 41, conductor 52, step H of the starting resistance, conductor l5, armature of motor 3, conductor 4 to the opposite line terminal. Operating coil 48 is now connected across the line through main contactor 8, conductor 9, conductor 4|, contact 38, bridging member 37, flexible lead 5|, conductor 49, operating coil 48, conductor 48 to switch l4 and conductor I3 to the opposite side of the line. The operation of this second step of the acceleration is similar to that previously described. If the motor continues to build up the speed, the armature current will decrease until lockout coil 4! no longer counteracts the action of operating coil 48 whereupon bridging member 44 will complete a circuit through contacts l8 and 43 connecting the motor directly to the line terminals and shunting out bimetal 54 and lockout coil 41. The operation of the starter as above defined has been pure current limit which is the normal operation of the starter. If the motor 3 should not start or build up in speed sufficiently to reduce the armature current to a point where lockout coil 22 will no longer counteract the closing action of operating coil 34, current will continue to flow through'resistor ll until bimetal 24 becomes heated to a point where it flexes and engages contacts 25 and 28. This closes the shunt across lockout coil 22 whereupon operating coil 34 moves armature 38 and member 31 into their bridging position regardless of the value of the current flowing through the motor armature thus cutting out step l8 of resistance II. It the motor still does not start or if the armature current is still high enough to prevent operating coil 48 from closing ill contacts 43 and I8, current will continue to flow 1i i through step I! of the starting resistance until bimetal 54 causes contacts 58 and 51 to engage whereupon lockout coil 41 will be shunted out and bridging member 44 will be operated to cut out resistance step I! and connect motor directly 1 to the line. The latter described operation is an abnormal one which is intended to function only when the armature current does not decrease quickly enough to a value where the lockout coil becomes ineffective. This provides for a positive time limit acceleration by cutting out the steps of the starting resistance after a predetermined time interval if the armature current is too high to permit of normal current acceleration. This prevents a burning up of resistance H by positively shunting steps l8 and I! out of the motor circuit regardless oi the values of the armature current.

The starter as just described has obvious advantages over the current limit starter or the time limit starter. In the current limit starter, if the motor current does not decrease to a predetermined value the starting resistance will be left in the circuit until it burns out and is destroyed. In the time limit starter the periods of operation 01' the resistance steps are fixed and thus in normal operation a greater time interval will be taken in starting the motor than is necessary. In the starter as above described the time required to start the motor will always be at a desired minimum since under normal operating conditions the current limit portion of the starter will operate to cut out resistance and bring the motor up tospeed in the shortest time interval corresponding to their current settings and it is only when the armature current does not decrease to the set value that the time limit portion of the starter operates to positively shunt out steps of the starting resistance. While the starter is illustrated and described as employing a bimetal 24, it is obvious;

that any other type of time limit relay could be substituted therefor although the bimetal is preferred since its time of operation is dependent upon the current flowing therethrough and in herently embodies the additional protective fee.-

ture of cutting out the resistance with a time interval which will depend to some extent on the value of the current flowing therethrough. However, othertime limit relays could be substituted therefor to secure the desired current and time limit features and as examples thereof there could be used a magnetic relay with a dash pot or an indirectly heated thermal relay or any other form of time limit relay.

Figure 2 illustrates another embodiment of the invention peculiarly adapted for larger motors. Like reference numerals refer to parts similar to those shown in Figure 1. In this figure resistance I1 is divided into three accelerating steps; three combined current and time limit relays being provided to cut out these steps. In this embodiment the thermal element and lockout coils do not carry the full motor current but are connected in parallel with the corresponding steps of the starting resistance and their circuits contain an added resistance to control the division of currents between the starting resistance and the control circuits. In this figure there are line terminals l and 2 and a main contactor 8 having stationary and movable contacts 28 and 29, an operating coil II and auxiliary contacts 3| and 32. A switch I4 is provided, one side of which is connected to line terminal I, by conductor l3, the other side of which is connected to operating coil I l by conductor I2 and to the operating coils 34, 46' and 46 for the bridging contactors through conductors and 48 and 48. The other side of coil 34 is connected to contact 32 by conductor 33. The other side of coil 46' is connected to bridging member 31 by conductor 49' and flexible lead 5|. The opposite side of coil 46 is connected to conducting member 44' by conductor 49 and flexible lead 5|. The lockout coils and thermal elements are connected in series with each other and with resistances El, 62 and 63. Lockout coil 22 is connected in series with bimetal 24 and resistor 6|, the bimetal controlled shunt circuit 23, 25, 26 and 21 being provided for thelockout coil 22. This circult is connected at one side to the line 2 through conductor 9 and the main contactor 3. The opposite side of this control circuit is connected to contact 39 and thence to the .end of the first accelerating step l8 of the starting resistance. The control circuit is thus placed in parallel with step l8 of the starting resistance. The control circult for the second accelerating step embodying the lookout coil 41', bimetal 54 and resistance 62 is connected at one side to conductor 49' and at the other side to contact l6 thus placing it in parallel with the second step IQ of the starting resistance. The bimetal controlled shunt circuit 53, 56', 51 and 53' is provided for lockout coil 41'. The control for the third accelerating step embodying lockout coil 41, bimetal 54, resistance 63, is connected at one side to conductor 49 and'at its opposite side to conductor l5 leading to the motor and is thus placed in parallel with the last step I9 of the starting resistance. The lockout coil 4'! is provided with the bimetal controlled shunt circuit 53, 56, 51 and 58. The operation of the starter shown in Figure 2 is similar to that shown in Figure 1 and it is thought unnecessary to take the space necessary to describe it in detail since it is readily apparent from the description of the operation of the starter in Figure 1; the only difference being that here there are shown three accelerating steps and each control circuitcan ries only a fraction of the total motor current since each is connected in parallel with the corresponding step of the starting resistance. The

parallel arrangement of Figure 2 is particularly adapted to large size motors due to practical limitations .in the size of the thermal elements and in the current carrying capacity of the short-circuiting contacts of the thermal relay.

While Figure l is showing two accelerating steps and Figure 2 is disclosing three accelerating steps it is obvious that in either-form any number of accelerating steps may be used to secure the desired starting characteristics.

While certain preferred embodiments of the invention have been specifically disclosed, it is understood that the invention is not limited thereto as many variations will be readily apparent to those skilled in the art and the invention is to be given its broadest possible interpretation within the terms of the following claims:

1. The method of starting a motor which comprises connecting said motor to the line through a starting resistance, short-circuiting said starting resistance if and when the motor current decreases to a predetermined value, and shortcircuiting said starting resistance after a predetermined time interval .when the motor current fails to decrease to said value.

2. The method of starting a motor which comprises connecting the motor to a line through a starting resistance, short-circuiting said starting resistance if the motor current decreases to a predetermined value within a predetermined time interval, and short-circuiting said starting resistance at the end of said time interval regardless of the failure of the motor current to decrease to said value.

3. An electrical relay comprising relatively movable contacts, means for operating said contacts, current responsive means restraining operation of said contacts and means for automatically rendering said restraining means ineffective.

4. In an automatic starter for electric motors, a starting resistance, an accelerating contactor adapted to shunt out at least a part of said starting resistance, an operating coil for said eontactor, current responsive means restraining operation of said contactor, and means for automatically rendering said restraining means ineffective.

5. In an automatic starter for electric motors, a starting resistance, a contactor adapted to shunt out at least a part of said starting resistance, a shunt coil normally urging said contactor to closed position, a lockout coil responsive to the motor current normally urging said contactor to open position and a time limit relay connected to short-circuit said lockout coil when the contactor does not close after a predetermined time interval.

6. In an automatic starter for electric motors, a starting resistance, an accelerating contactor adapted to cut out at least a part of said starting resistance and means for actuating said contactor normally responsive to a predetermined value of starting current and actuating said contactor after a predetermined time interval when the starting current has failed to decrease to said value.

'7. In an automatic starter for electric motors, a starting resistance and an accelerating contactor for cutting out said starting resistance, means for operating said accelerating contactor when the starting current decreases to a predetermined value, said means operating said accelerating contactor after a predetermined time interval regardless of the failure of the starting current to decrease to said value.

8. An automatic controller for electric circuits comprising relatively movable contacts, an operating coil for biasing said contacts toward closed position, a current responsive lockout coil for biasing said contacts toward open position, a bi- -metallic element connected in series with said lockout coil, a contact carried by said bimetallic element, a second contact disposed adjacent to said first mentioned contact and in the path of movement thereof, said second contact being connected to the side of the lockout coil opposite to the one connected to the bimetallic member, the bimetallic element flexing to close the contacts and short-circuit the lockout coil when the relay fails to operate after predetermined time interval. 7

9. In an automatic starter for electric motors, a starting resistance divided into a plurality of accelerating steps, a plurality of accelerating contactors successively short-circuiting said steps, each contactor including an operating coil for biasing said contactor toward closed position, a lockout coil responsive to the current through the starting resistance for biasing said contactor toward open position, and a time limit relay short-circuiting said lockout coil when its as sociated contactor fails to function within a predetermined time interval.

10. An automatic starter for electric motors comprising a starting resistance, an accelerating contactor adapted to short-circuit at least a part of said resistance. an operating coil for biasing said contactor toward closed position, a current responsive lockout coil for biasing said contactor toward open position, a bimetallic element, an auxiliary resistance, said lockout coil, bimetallic element and auxiliary resistance being connected in series with each other and in parallel with at least a part of the starting resistance and a shunt for said lockout coil controlled by said himetallic element.

11. In an automatic starter for electric motors, a starting resistance, means for shunting said resistance from the circuit after a predetermined time interval, said means shunting said resistance before the expiration of said time interval when the motor current decreases to a predetermined value.

12. An automatic starter for electric motors comprising a starting resistance, means for shunting at least a part of said resistance when the motor current decreases to a predetermined value, and means operating to efiect shunting of at least a part of said resistance after a definite time interval upon the failure of the motor current to decrease to said value.

13. An automatic starter for electric motors comprising a starting resistance, means responsive to the current through the motor for shunting at least a part of said resistance when the current decreases to a predetermined value and a time delay relay operating to effect shunting of at least a part of said resistance after a definite time interval upon the failure of the motor current to decrease to said value.

14. In an automatic starter for electric motors, a starting resistance, a contactor connected to shunt at least a part of said resistance from the motor circuit, means biasing said contactor toward closed position, a current responsive coil biasing said contactor to open position, and a time limit relay operating to short-circuit said coil if contactor does not operate after a definite time interval.

15. An automatic controller for electric circuits comprising relatively movable contacts, means for biasing said contacts toward closed position, current responsive means for biasing said contacts toward open position, a normally open shunt for the current responsive means, and means to close said shunt circuit when said contacts fail to close after a definite time interval.

16. An automatic controller for electric circuits comprising relatively movable contacts, an operating coil for biasing said contacts toward closed position, a current responsive lockout coil for biasing said contacts toward open position, a normally open shunt circuit for said lockout coil and a current responsive element connected in series with said lockout coil for closing said shunt circuit.

17. An automatic controller for electric circuits comprising relatively movable contacts, an operating coil for biasing said contacts toward closed position, a current responsive lockout coil for biasing said contacts toward open position,

a thermostatic element connected in series of said lockout coil, and a shunt circuit for said lockout coil closed by said thermostatic element.

18. In an automatic controller for electric circuits comprising relatively movable contacts, an operating coil for biasing said contacts toward closed position, a current responsive lockout coil for biasing said contacts toward open position, and a bimetallic element connected in series with said lockout coil, said element operating to shortcircuit the lockout coil when the contacts fail to close after a definite time interval.

19. An automatic starter for electric motors comprising a starting resistance, an accelerating contactor adapted to shunt out at least a part of said starting resistance, an operating coil for biasing said contactor toward closed position, a current responsive lockout coil for biasing said contactor toward open position, an auxiliary resistance, said lockout coil being connected in parallel with at least a part of said starting resistance through an auxiliary resistance, and a time limit relay short-circuiting said lockout coil when said contactor fails to close after a definite time interval.

20. In an automatic starter for electric motors,

a starting resistance adapted to be connected in series with a motor armature, and means for automatically shunting out at least a portion of said resistance, said means functioning when the motor current decreases to a predetermined value within a definite time interval, said means functioning at the end of said interval regardless of the failure of the motor current to decrease to said value.

21. An automatic starter for electric motors, comprising a starting resistance, a normally open shunt circuit for at least a part of said resistance, a contactor for closing said shunt circuit, and means for operating said contactor when motor current decreases to a predetermined value, said means operating said contactor at the end of a definite time interval when the motor current fails to decrease to said value.

22. An automatic starter for electric motors comprising a starting resistance, a contactor operating to shunt out at least a part of said starting resistance, an operating coil for biasing said contactor toward closed position, a current responsive lockout coil for restraining operation of said contactor, a thermostatic element connected in series with said lockout coil and a shunt circuit for said lockout coil adapted to be closed by said thermostatic element.

23. An automatic starter for electric motors comprising a starting resistance, a contactor operating to shunt out at least a part of said starting resistance, a shunt coil for operating said contactor, a current responsive lockout coil for preventing operation of said contactor, a bimotallic element connected in series with said lockout coil, said element short-circuiting said lockout coil when the contactor fails to operate after a definite time interval.

24. An automatic starter for electric motors comprising a starting resistance divided into a plurality of accelerating steps, a plurality of accelerating contactors for successively short-circuiting said steps, each contactor including a shunt operating coil, a current responsive lockout coil and a time limit relay for short-circuiting said lockout coil when the associated contactor fails to function within a definite time interval after being energized, the closing of each contactor energizing the shunt coil, lockout coil, and time limit relay of the next succeeding contactor.

25. An automatic starter for electric motors comprising a starting resistance divided into a plurality of accelerating steps, a plurality of accelerating contactors for successively short-circuiting said steps, each contactor including a shunt operating coil, a current responsive lockout coil and a time limit relay for short-circuiting the lockout coil when the associated contac tor fails to operate within a definite time interval after being energized, said lockout coil and time limit relay being connected in series with each other and in parallel with the associated step of the starting resistance, the closing of each con tactor operating to energize the operating coil, lockout coil, and time limit relay of the next succeeding contactor in the accelerating series. 26. The method of starting an electric motor through a starting resistance which is shunted from the circuit after the starting period to connect the motor directly to the line, which comprises connecting a motor to a line through a starting resistance and shunting said resistance from the motor circuit at the minimum time consistent with a desired maximum overload and, failing decrease to said maximum overload, after a maximum set time.

27. The method of starting an electric motor to secure a starting time having the minimum value consistent with a desired maximum overload and a maximum set value which comprises connecting said motor to a line through a start ing resistance and shunting at least a part of said resistance from the circuit if and when the motor current decreases to a predetermined value and, failing such decrease, after a definite time interval independent of the value of the current.

HERMON L. VAN VALKENBURG. 

